The purpose of this work is to examine the chemical and biological properties of murine histocompatibility antigens (H-2) and tumor associated transplantation antigens (TATA). The approach is to purify the molecules expressing these antigens and determine their properties at each stage of purification and when they are reconstituted into artificial membranes composed of lipid and other highly purified proteins. The properties examined include: 1) ability to induce in vivo transplantation rejection and humoral response, 2) ability to stimulate cytotoxic T lymphocytes in vitro, 3) chemical properties with particular emphasis on how these molecules bind to biological membranes, 4) the metabolism of these antigens in normal and neoplastic cells. The rationale for this approach is that by examining the behavior of these molecules in simple reconstituted membranes, an understanding can be gained of how these molecules interact with receptors on lymphoid cells in order to express their known biological effects on T cell mediated immune reactions (H-2). Furthermore, knowledge of the biological properties of these molecules will provide a rational basis for using them in in vivo therapeutic protocols.